Doctors worried about unusual strains of HIV

Lisa M. Krieger, EXAMINER MEDICAL WRITER

Published 4:00 am, Friday, July 12, 1996

1996-07-12 04:00:00 PDT VANCOUVER, BRITISH COLUMBIA -- VANCOUVER, B.C. - Almost one-fifth of newly identified HIV infections in an inner-city New York hospital involved unusual strains of the virus not previously seen in the United States and thought to have originated in Africa and Asia, a federal expert says.

But nevertheless, "the high prevalence of unusual serotypes has important public health implications," Irvin said.

There is concern, she said, that genetic differences in HIV subtypes could affect U.S. rates of transmission and responses to therapy and vaccines.

The CDC team studied patients admitted to Bronx Lebanon Hospital Center, a large public hospital in South Bronx, N.Y., a poor and urban community with one of the highest prevalences of HIV infection in the United States. It also has one of the highest proportions of immigrants and visitors from the Caribbean, Latin America and Africa.

The researchers found that eight of the 43 infected patients studied - 18.6 percent - had viral types different from the North American subtype B. They found, instead, subtype A, common in India; subtype B, Thailand; and three instances of subtype C, Brazil and India.

There is a chance these subtypes have spread because at least six of the eight patients reported recent unprotected sex.

Of concern to public health experts is the fact that nearly all commercially available HIV tests used for diagnosis and screening blood in the United States are based on the domestic strain. The ability of these to detect unusual strains is untested, Irvin said.

There are also studies suggesting that while the U.S. strain of the human immunodeficiency virus is more likely to be passed on during gay sex, the African and Asian strains tend to be transmitted heterosexually.

If so, public health experts worry that the United States is vulnerable to a heterosexual epidemic much larger than what has been seen so far.

During the past six years, McCutchan's team has genetically characterized the HIV strains that are prevalent in centers of the pandemic where the majority of new infections are occurring. McCutchan's team discovered that most geographic locales, including the United States and Europe, have at least some mixture of subtypes.

"We can presume that the human propensity for travel and relocation will lead to an increasing intermixing of HIV subtypes in the future," she said.&lt;